Electrochemical energy storage devices include primary (disposable) and secondary (rechargeable) batteries of almost any type, including but not limited to alkali ion and alkaline earth ion batteries and flow batteries as described in U.S. Provisional Patent Application Ser. Nos. 61/912,215, filed on Dec. 5, 2013, 61/911,101, filed on Dec. 3, 2013, 61/903,574 filed on Nov. 13, 2013, 61/903,739 filed on Nov. 13, 2013, 61/892,588, filed on Oct. 18, 2013, 61/831,321, U.S. patent application Ser. No. 14/172,648, filed on Dec. 4, 2014, Ser. No. 13/083,167, filed on Apr. 8, 2011, Ser. No. 12/970,753, filed on Dec. 16, 2010, Ser. No. 13/404,735 (now U.S. Pat. No. 8,582,807), filed on Feb. 24, 2012, and U.S. Pat. No. 7,338,734, filed on Dec. 23, 2002, U.S. Pat. No. 8,722,227, filed on Aug. 26, 2013, U.S. Pat. No. 8,148,013, filed on Sep. 17, 2007, each of which is hereby incorporated by reference in its entirety.
Fuel cells include any fuel cell type in which at least one of the fuels or reactants is a condensed phase, including instances where the fuel is liquid or semi-solid, and where the fuel cell uses a physical membrane or is “membraneless” with electronic isolation of the electroactive reactants being achieved through controlled flow of one or more fluid phases.
A battery stores electrochemical energy by separating two half cells (e.g., a conductive electrode and surrounding conductive electrolytes) with different electro-chemical potential. Each half-cell has an electromotive force, determined by its ability to drive electric current from the interior to the exterior of the cell. A difference in electrochemical potentials and/or electromotive forces generates an electric current when a conductive material connects the electrodes.
Rechargeable batteries can be constructed using static negative electrode/electrolyte and positive electrode/electrolyte media. Rechargeable batteries can be restored (e.g., recharged) by applying reverse current and/or voltage. Lead-acid batteries used in vehicles and lithium ion batteries for portable electronics are some examples of rechargeable batteries. In rechargeable batteries, the electrode active materials generally need to be able to accept (e.g., to be charged) and provide (e.g., to discharge) ions.
A flow battery is a rechargeable battery that has soluble metal ions in liquid solutions. The ability of a flow battery to be recharged is generally provided by oxidation and reduction of two flowing electrolyte liquids separated by a membrane. A flow battery typically includes reservoirs for storing electrolytes, a membrane for ion exchange, and pumps for controlling flow of the electrolytes.
Redox flow batteries, also referred to as flow cells, redox batteries, or reversible fuel cells are energy storage devices in which the positive and negative electrode reactants are soluble metal ions in liquid solution that are oxidized or reduced during the operation of the cell. Using two reversible redox couples, liquid state redox reactions are carried out at the positive and negative electrodes. A redox flow cell typically has a power-generating assembly comprising at least an ionically transporting membrane separating the positive and negative electrode reactants (also called catholyte and anolyte respectively), and positive and negative current collectors (also called electrodes) which facilitate the transfer of electrons to the external circuit but do not participate in the redox reaction (i.e., the current collector materials themselves do not undergo Faradaic activity). Redox flow batteries have been discussed, for example, by C. Ponce de Leon, A. Frias-Ferrer, J. Gonzalez-Garcia, D. A. Szantos and F. C. Walsh, “Redox Flow Batteries for Energy Conversion,” J. Power Sources, 160, 716 (2006), M. Bartolozzi, “Development of Redox Flow Batteries: A Historical Bibliography,” J. Power Sources, 27, 219 (1989), and by M. Skyllas-Kazacos and F. Grossmith, “Efficient Vanadium Redox Flow Cell,” Journal of the Electrochemical Society, 134, 2950 (1987).
Some batteries (e.g., flow batteries) have significant pumping losses due to a variety of factors, including a combination of high flow electrode viscosity, high flow velocity during operation, and/or narrow channel cross-sectional dimensions and/or long channel length. Some flow batteries utilize flow electrodes with non-Newtonian rheology (e.g., yield-stress fluids), for example, the high energy density flow electrodes described in U.S. Provisional Patent Application Ser. Nos. 61/892,588, filed on Oct. 18, 2013, 61/903,574, filed on Nov. 13, 2013, 61/903,739, filed on Nov. 13, 2013, U.S. patent application Ser. No. 12/970,753, filed on Dec. 16, 2010, U.S. Pat. No. 8,722,227, filed on Aug. 26, 2013, each of which is incorporated herein by reference in its entirety and publications M. Duduta, B. Y. Ho, V. C. Wood, P. Limthongkul, V. E. Brunini, W. C. Carter, Y.-M. Chiang, “Semi-Solid Lithium Rechargeable Flow Battery,” Adv. Energy Mater., 1[4] 511-516 (2011) (DOI: 10.1002/aenm.201100152) and F. Y. Fan, W. H. Woodford, Z. Li, N. Baram. K. C. Smith, A. Helal, G. H. McKinley, W. C. Carter, Y.-M. Chiang, “Polysulfide Flow Batteries Enabled by Percolating Nanoscale Conductor Networks,” Nano Letters, 5 Mar. 2014, DOI: 10.1021/n1500740t, the disclosure of each of these publications being incorporated herein by reference in its entirety.
In some instances, the flow electrodes have a continuous percolating network of an electronic conductor phase that imparts electronic conductivity to the flow electrodes. The rheology of the flow electrodes may be non-Newtonian by possessing, for example, shear-thinning behavior, or Bingham plastic or Hershel-Bulkley rheology wherein there is a measurable yield stress to the fluid followed by Newtonian or non-Newtonian viscosity after the yields stress is overcome. High energy density fluid electrodes for high energy density flow batteries typically have non-Newtonian rheology, especially when formulated as suspensions which increase electrical conductivity, energy density, or both. The rheology of the flow electrodes can result in significant pumping energy losses and/or decreases in electrochemical energy efficiency (e.g., in a flow battery).
Thus, there is a need for improved articles and methods for promoting flow of electroactive phases of electrochemical devices. For example, there is a need for robust surfaces that promote electrode flow in batteries.